I liked it, it's short and simple, and one can really see the point of the poem easily. I'm not so sure the title -The Eighth Deadly Sin- fits with the poem, but that's just me.
Unloved_Misery
Someday I'll try to figure out
Which class
you should be in:
Did
I hate when
I should've loved,
Or is misplaced love still
my sin?
And one more thing... in the second stanza I wasn't sure who you were referring to, because the first part goes "Someday I'll try to figure out Which class you should be in:" but the second part you seem to be asking yourself the question, and not the "you" you mentioned. Just wondering.